Computer systems have benefited from several different advances in technology that have taken place over the last several decades. One of the most important advances has come in integrated circuit fabrication technology, especially for complementary metal-oxide-semiconductor (CMOS) technology. Modern CMOS technology has allowed the development of high-speed, low-power and low-voltage integrated circuits. One type of integrated circuit that has benefited from improvements in CMOS technology is integrated circuit memory. In order to take full advantage of the speed capabilities of CMOS technology, the Joint Electron Devices Engineering Counsel (JEDEC) has developed specifications for computer memory integrated circuits that operate at very high clock speeds, for example several gigahertz (GHz), and that can transfer data on both edges of the clock signal.
However when operating at speeds as high as several GHz, integrated circuit memories require receivers that are sensitive enough to capture the correct logic state of the data when the difference between a logic high state and the logic low state is only a few hundred millivolts (mV). Because of the small voltage swing, transmission and reception of data is susceptible to different environmental factors that can cause data transmission failure. One of those factors is noise that includes not only random energy fluctuations but also electromagnetic interference (EMI) absorbed from the surrounding environment. To reduce the occurrence of reception errors and increase memory operating speed, therefore, it would be useful to reduce the sensitivity of integrated circuits to environmental noise.
In the following description, the use of the same reference numerals in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.